Cryogenic refrigerator

ABSTRACT

A cryogenic refrigerator includes a pressure switching valve with a rotational element for switching between channels. The cryogenic refrigerator includes a first member located on one side in a direction of a rotational axis of the rotational element; a second member located on another side in the direction of the rotational axis of the rotational element; a bearing rotatably supporting the rotational element; and an elastic element. The first and second members sandwich the bearing via the elastic element.

FIELD

The disclosures herein relate to a cryogenic refrigerator including a bearing which holds a pressure switching valve whose rotational element is rotated to switch between channels.

BACKGROUND

Japanese Laid-open Patent Publication No. 2004-53157 discloses a pressure switching valve whose rotational element for switching between channels is held by a bearing, wherein an elastic element is inserted between the rotational element and the bearing in a radial direction such that the rotation of the rotational element rotates the bearing with reliability.

In the case of a configuration in which an outer race of the bearing is secured by sandwiching the outer race of the bearing between two members disposed in a direction of a rotational axis, there may be a case where the outer race of the bearing is not secured with reliability due to processing tolerances, etc., unless these two members are processed with high accuracy. If the outer race of the bearing is not secured and thus is rotated, wear occurs in a member which supports the outer race of the bearing from an outer surface side in the radial direction, which results in a problem that complicated processes are necessary for the processing of these two members.

SUMMARY

According to an aspect of the embodiment, a cryogenic refrigerator is provided. The cryogenic refrigerator includes

a pressure switching valve with a rotational element for switching between channels;

a first member located on one side in a direction of a rotational axis of the rotational element;

a second member located on another side in the direction of the rotational axis of the rotational element;

a bearing rotatably supporting the rotational element; and

an elastic element, wherein

the first and second members sandwich the bearing therebetween via the elastic element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing illustrating an example of an overall configuration related to a cryogenic refrigerator;

FIG. 2 is a cross-section view of an example of a main portion of a cryogenic refrigerator 14; and

FIG. 3 is a cross-section view of another example of a main portion of a cryogenic refrigerator 14′.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described with reference to the accompanying drawings.

FIG. 1 is a drawing illustrating an example of an overall configuration related to a cryogenic refrigerator.

The configuration illustrated in FIG. 1 includes a gas compressor (merely referred to as a compressor, hereinafter) 10 which includes a suction port 10A for receiving operation gas (a refrigerant gas) and a discharge port 10B for discharging the compressed operation gas; and a cryogenic refrigerator 14 coupled to the compressor 10. In FIG. 1, a low-pressure pipe is indicated by the numeral reference 16 and a high-pressure pipe is indicated by the numeral reference 18.

FIG. 2 is a cross-section view of an example of a main portion of the cryogenic refrigerator 14.

The cryogenic refrigerator 14 is a Gifford McMahon cycle (GM) refrigerator. The GM refrigerator utilizes a change in volume of space induced by a displacer reciprocating in a cylinder to obtain a cooling effect based on the Gifford McMahon refrigeration cycle. It is noted that according to the GM refrigerator, a high-pressure refrigerant gas (He gas, etc.) is supplied to the cylinder in which the gas is adiabatically expanded to obtain a cryogenic temperature. The expanded cryogenic-temperature refrigerant gas absorbs heat from the surroundings and is exhausted from the cylinder after the temperature of the refrigerant gas is increased to a room temperature by thermal exchange with a storage medium. In this way, the inside of the cylinder is kept at a cryogenic temperature. The refrigerant gas exhausted from the cylinder is supplied to the compressor in which it is compressed to be the high-pressure refrigerant gas. The high-pressure refrigerant gas is supplied to the cylinder of the GM refrigerator again.

The cryogenic refrigerator 14 mainly includes a cylinder section 20, a valve body 30, a valve plate 34, a bearing 36, a lid member 50, a housing 60, and a motor 46, as illustrated in FIG. 2.

The cylinder section 20 may define any number of stages such as one stage, two stages, etc. It is noted that a configuration of the cylinder section 20 itself may be arbitrary and is not explained in detail here.

The housing 60 accommodates therein various components of a rotary valve (the valve body 30, the valve plate 34, the bearing 36, etc.), etc.

The lid member 50 is provided such that it covers an opening on one side of the housing 60 (in the illustrated example, an opening on an upper side). The lid member 50 is fastened to the housing with bolts 80. The bolts 80 are tighten with a relatively high tightening torque so as to prevent looseness of the bolts 80. Further, O-rings 72A, 72B are provided between the lid member 50 and the housing 60 so as to ensure hermeticity. A high-pressure channel 50A to be coupled to the high-pressure pipe 18 is formed in the lid member 50.

The motor 46 is provided such that it covers an opening on another side of the housing 60 (in the illustrated example, an opening on a lower side). An O-ring 46C is provided between a motor housing of the motor 46 and the housing 60 so as to ensure hermeticity. It is noted that the inside of the motor 46 is coupled to the suction port 10A on the low-pressure side of the compressor 10 via the low-pressure pipe 16. The motor 46 includes a rotational shaft 46A. The rotational movement of the rotational shaft 46A of the motor 46 causes a rotational movement of the valve plate 34 via a crank 46B and an eccentric pin 46D, and a reciprocating movement of a displacer 21 via a Scotch yoke 92.

The cylinder section 20 is hermetically coupled to a side portion of the housing 60. A fluid channel 60B is formed in the side portion of the housing 60. A fluid channel 50B corresponding to the fluid channel 60B is formed in the lid member 50.

The valve body 30 is disposed in a concave portion formed on the inner side (i.e., a lower surface) of the lid member 50. The valve body 30 is installed such that it is not rotatable with respect to the lid member 50. O-rings 32 are provided between the outer surface of the valve body 30 and the lid member 50. A high-pressure fluid channel 30B is formed in the valve body 30 such that it passes through a center portion of the valve body 30. The high-pressure fluid channel 30B is in fluid communication with the high-pressure pipe 18 via the high-pressure fluid channel 50A of the lid member 50. The valve body 30 has a valve side fluid channel 30C and a cylinder side fluid channel 30A formed therein which are in fluid communication with the fluid channels 60B and 50B. The valve body 30 is biased toward the valve plate 34 with a spring 31 which is provided between the valve body 30 and the lid member 50.

The valve plate 34 is a rotational element coupled to the rotational shaft 46A of the motor 46. The valve plate 34 is provided such that it slidably abuts the valve body 30. The side of the valve plate 34, which comes into contact with the valve body 30, has a high-pressure fluid channel 34B formed therein which has a bottom (a form of a groove or a concave portion). The high-pressure fluid channel 34B of the valve plate 34 is in fluid communication with the high-pressure pipe 18 via the high-pressure fluid channel 30B of the valve body 30 and the high-pressure fluid channel 50A of the lid member 50. Further, the valve plate 34 has a low-pressure fluid channel 34A formed therein which passes through the valve plate 34 in a direction parallel with the direction of the rotational axis. When the valve plate 34 rotates, the valve side fluid channel 30C and the cylinder side fluid channel 30A of the valve body 30 come in fluid communication with the high-pressure fluid channel 34B and the low-pressure fluid channel 34A alternately, thereby the directions of the refrigeration medium gas are switched alternately.

When the valve side fluid channel 30C and the cylinder side fluid channel 30A of the valve body 30 are in fluid communication with the high-pressure fluid channel 34B, the refrigerant gas from the compressor 10 is introduced into an upper chamber 90 of the cylinder section 20. When the valve side fluid channel 30C and the cylinder side fluid channel 30A of the valve body 30 are in fluid communication with the low-pressure fluid channel 34A, the refrigerant gas in the upper chamber 90 is collected by the compressor 10 via the inside of the motor 46. Thus, when the valve plate 34 is rotated, the introduction of the refrigerant gas into the upper chamber 90 (charging) and the recovery of the refrigerant gas from the upper chamber 90 (exhaust) are repeated. The repetition of introduction and recovery of the refrigerant gas and the reciprocating movement of the displacer 21 of the cylinder section 20 are synchronized with the rotation of the crank 46B. If a phase of the repetition of introduction and recovery of the refrigerant gas and a phase of the reciprocating movement of the displacer 21 are adjusted appropriately, the temperature of the refrigerant gas in an expansion chamber (not illustrated) of the cylinder section 20 reaches a cryogenic temperature and an endothermic effect is generated.

The valve plate 34 is rotatably supported by the housing 60 via the bearing 36, as illustrated in FIG. 2. The valve plate 34 has an outer surface fitted into an inner race 36B of the bearing 36. It is noted that the valve plate 34 includes a flange portion 34F at a rim on the valve body 30 side, and an axial registration is made at the flange portion 34F by a pressing force from the fitted inner race 36B.

The bearing 36 includes an outer race 36A, the inner race 36B and balls 36C. The bearing 36 is provided between the lid member 50 and the housing 60, as illustrated in FIG. 2. Specifically, the bearing 36 is fitted in the housing 60 such that the outer surface of the outer race 36A comes in contact with the inner surface of the housing 60. The inner surface of the housing 60 has a support surface 60A formed therein which projects toward the center side. The end surface of the outer race 36A of the bearing 36 is supported by the support surface 60A and the load in the direction of the rotational axis is carried by the housing 60 via the support surface 60A. The lid member 50 is provided such that the outer race 36A of the bearing 36 is sandwiched between the lid member 50 and the support surface 60A of the housing 60. The lid member 50 is provided such that it comes into contact with the end surface of the outer race 36A in the direction of the rotational axis via the O-ring 70, as illustrated in FIG. 2. In other words, the end surface of the outer race 36A comes into contact with the lid member 50 not directly but via the O-ring 70. The O-ring 70 is provided such that it comes into contact with the inner surface of the housing 60. The O-ring 70 has substantially the same diameter as the inner surface of the housing 60.

In this way, according to the embodiment, in order to support the bearing 36 between the lid member 50 and the housing 60 in the direction of the rotational axis, the O-ring 70 is provided between the lid member 50 and the housing 60 in the direction of the rotational axis. Thus, even in the case where there could be a clearance (space) between the housing 60 and the lid member 50 due to the processing tolerance, etc., of the housing 60 and the lid member 50, the clearance is filled with the O-ring 70. Thus, when the outer race 36A of the bearing 36 is installed, it is possible to appropriately apply a preload to the outer race 36A of the bearing 36 via the O-ring 70. Correspondingly, it is possible to prevent problems due to the space between the housing 60 and the lid member 50. In particular, the problems include such that the outer race 36A of the bearing 36 is not secured and thus is rotated, resulting in abrasion of the housing 60. It is noted that the preload acting on the outer race 36A of the bearing 36 can be easily adjusted by adjusting the distance between the housing 60 and the lid member 50 (i.e., the distance in the direction of the rotational axis) or the elastic property of the O-ring 70.

According to the embodiment described above, the following effect among others can be obtained.

According to the embodiment, as described above, by providing the elastic element such the O-ring 70 between the housing 60 and the lid member 50, an appropriate preload can be applied to the outer race 36A of the bearing 36. As a result of this, it is possible to prevent with reliability the problems which could be induced due the dimensional tolerance or the processing tolerance of the housing 60 and the lid member 50 while reducing the processing cost.

Further, according to the embodiment, the lid member 50 is provided such that it has not only a function of covering the housing but also a function of securing the outer race 36A of the bearing 36. With this arrangement, it is possible to obviate the need for a plate for securing the bearing outer race and thus reduce the number of parts and the cost. Here, the lid member 50 may be fastened using a relatively great number of the bolts 80 in order that the lid member 50 can function safely as a lid of a pressure container. If an imbalance occurs between the tightening torques of these bolts 80, the bearing 36 may tilt. In this connection, according to the embodiment, as described above, when the bearing 36 is supported between the lid member 50 and the housing 60 in the direction of the rotational axis, the O-ring 70 is provided between the lid member 50 and the housing in the direction of the rotational axis. Thus, the O-ring 70 is deformed elastically when the bolts are tighten. Therefore, it is possible to prevent an excessive load from acting on the outer race 36A of the bearing 36. Further, the O-ring 70 is deformed elastically even when the imbalance occurs between the tightening torques. Therefore, it is possible to prevent the bearing 36 from tilting.

FIG. 3 is a cross-section view of another example of a main portion of a cryogenic refrigerator 14′.

The cryogenic refrigerator 14′ illustrated in FIG. 3 is the same as the cryogenic refrigerator 14 illustrated in FIG. 2 except for the location of the O-ring 70. Specifically, the cryogenic refrigerator 14 illustrated in FIG. 2 has the O-ring 70 between the housing 60 and the lid member 50 such that the O-ring 70 comes into contact with the lid member 50. To the contrary, the cryogenic refrigerator 14′ illustrated in FIG. 3 has the O-ring 70 between the housing 60 and the lid member 50 such that the O-ring 70 comes into contact with the housing 60. In other words, according to the cryogenic refrigerator 14 illustrated in FIG. 2, the outer race 36A of the bearing 36 is directly supported by the support surface 60A of the housing 60. To the contrary, according to the cryogenic refrigerator 14′ illustrated in FIG. 3, the outer race 36A of the bearing 36 is supported by the support surface 60A of the housing 60 via the O-ring 70. According to the cryogenic refrigerator 14′ illustrated in FIG. 3, it is possible to obtain the same effects as is the case with the cryogenic refrigerator 14 illustrated in FIG. 2. However, according to the cryogenic refrigerator 14 illustrated in FIG. 2, since the outer race 36A of the bearing 36 is directly supported by the support surface 60A of the housing 60, there is an advantage that the axial position of the bearing 36 with respect to the housing 60 can be determined precisely.

Preferably, in the cryogenic refrigerator 14 illustrated in FIG. 2, the O-ring 70 is provided such that it contributes to the hermeticity between the housing 60 and the lid member 50. In the illustrated example, the O-ring 70 is elastically deformed between the housing 60 and the lid member and thus contributes to the hermeticity between the housing 60 and the lid member 50. Specifically, when the high-pressure refrigerant gas is supplied to the cryogenic refrigerator, the O-ring 70 provides a function of preventing a leak of the high-pressure refrigerant gas between the housing 60 and the lid member 50 (i.e., between the fluid channel 60B of the housing 60 and the fluid channel 50B of the lid member 50) to the low-pressure side space (i.e., the space within the housing 60 which is in fluid communication with the inside of the motor 46). Thus, if such a sealing function of the O-ring 70 is sufficient, it is possible to eliminate the O-ring 72A (see FIGS. 2 and 3) which implements the same function.

The present invention is disclosed with reference to the preferred embodiments. However, it should be understood that the present invention is not limited to the above-described embodiments, and variations and modifications may be made without departing from the scope of the present invention.

For example, according to the embodiment, the O-ring 70 is disclosed as an example of an elastic element; however, elastic elements other than the O-ring 70 may be used as long as they are elastic parts (for example, parts made of a resin, rubber or the like). For example, a wave washer, a sealing member having a cross section of U-shape, such as a U-seal (registered trade mark) or the like may be used.

Further, according to the embodiment, the lid member 50 is provided such that it provides a function of securing the outer race 36A of the bearing 36, thereby the plate for securing the bearing outer race is eliminated. However, the configuration in which the outer race 36A of the bearing 36 is secured using another member, such as the plate for securing the bearing outer race, instead of the lid member 50 is also applicable. In this case, the outer race 36A of the bearing 36 may be secured between the other member, such as the plate for securing the bearing outer race, and the housing 60 via the O-ring 70. Further, the housing 60 may be replaced with the other member.

Further, according to the embodiment, the configuration in which the Gifford McMahon cycle (GM) is adopted is described as an example; however, any type of a cryogenic refrigerator, such as a pulse tube refrigerator, for example, is also applicable. In the case of the pulse tube refrigerator, the configuration described above may be applied in a rotary valve accommodating section (i.e., a housing section) upstream of the pulse tube refrigerator.

The present application is based on Japanese Priority Application No. 2010-194989, filed on Aug. 31, 2010, the entire contents of which are hereby incorporated by reference. 

What is claimed is:
 1. A cryogenic refrigerator comprising: a pressure switching valve with a rotational element for switching between channels; a first member located on one side in a direction of a rotational axis of the rotational element; a second member located on another side in the direction of the rotational axis of the rotational element; a bearing rotatably supporting the rotational element; and an elastic element, wherein the first and second members sandwich the bearing therebetween via the elastic element.
 2. The cryogenic refrigerator as in claim 1, wherein the first and second members define a space for hermetically accommodating the rotational element.
 3. The cryogenic refrigerator as in claim 1, wherein the second member defines a housing for accommodating the bearing and the elastic element therein, the first member defines a lid member for the housing, and the elastic element is provided between the lid member and the bearing.
 4. The cryogenic refrigerator as in claim 2, wherein the second member defines a housing for accommodating the bearing and the elastic element therein, the first member defines a lid member for the housing, and the elastic element is provided between the lid member and the bearing.
 5. The cryogenic refrigerator as in claim 2, wherein the elastic element is provided such that it contributes to hermeticity of the space between the first and second members.
 6. The cryogenic refrigerator as in claim 3, wherein the elastic element is provided such that it contributes to hermeticity of a space between the first and second members.
 7. The cryogenic refrigerator as in claim 4, wherein the elastic element is provided such that it contributes to hermeticity of the space between the first and second members. 